"I love going and shopping for Christmas presents for everybody and making gifts for people and seeing their faces light up and surprising them; that's where I get my joy," the entertainer said last week.

It's also why Lopez launched her "J. Lo's Christmas Gift" drive, asking fans to donate to her three favorite charities (the Boys & Girls Club, the Children's Hospital of Los Angeles and the American Red Cross). In exchange, she'll give someone two tickets to the last show of her "Dance Again" world tour in Puerto Rico on Saturday; she'll also pay airfare and hotel costs.

"It's just that kind of doing something nice for somebody, and they do something nice back and kind of paying it forward," she said in a phone interview Friday from Australia, where she was performing

She's promoting the contest, which ends Monday, on Twitter with the hashtag JLOSCHRISTMASGIFT. She got the idea to use social media to encourage her fans to give back since becoming more involved in platforms like Twitter and Facebook and seeing how much response she's received when she's had contests.

"I thought, `What if every person I tweeted and asked for a follow donated a dollar?' I have 13 1/2 million followers (on Twitter)," she said. "We can collect a lot of money for these charities that I work with that are literally close to my heart."

Part of the reason Lopez chose the Red Cross is because of its relief work in the aftermath of Hurricane Sandy, which devastated parts of New York City, where Lopez is from. She hasn't been back to New York since the October storm but her ex-husband, Marc Anthony, was affected.

"My babies (4-year-old twins Max and Emme) had to go there and visit their dad shortly after, and it was like, kind of a scary proposition to send them because I didn't know what it was going to be like," she said. "He was saying how his house had a tree fall in his front yard, and he couldn't stay there and there was no electricity. Just knowing how so many people were affected by it and when you really hear the stats of it ... there's not enough you can do."

Lopez will be heading home for the holidays; Lopez said she feels blessed to have been able to stage her first world tour, particularly spending much of it with her family: "It's just been an amazing year."

Lopez said the tour was a "life-changing experience," but acknowledged it could also be grueling at times, with the constant travel. For that reason, she said she identified with Jenni Rivera, the Latin music superstar who was killed Dec. 8 in a plane crash. Rivera was traveling after a concert in Monterrey, Mexico.

"I didn't know her personally but I knew of her. For me, just being on tour right now, you live the same type of life. You know what I mean? It's traveling, it's doing shows," Lopez said. "She considered herself a businesswoman as well, besides an artist, and she had kids and I'm sure she was rushing home to get home to her kids at that time so she took the flight at 3 in the morning. So you go like, wow, it's just like a wake-up call for everybody. It's tragic. She was so young, so young, and she had five kids. It just wasn't her time, it feels like."